Traditionally, wire bonding or metal clip is used for interconnection in a power device. For example, as shown in FIGS. 1A to 1C of the present disclosure disclosed in FIGS. 1-5 of U.S. Pat. No. 6,870,254B1, a chip 15 is attached on a lead frame 11, then a metal clip 16 is attached on the chip 15 for connecting the electrode of the chip 15 with a pin 13 located close to the lead frame 11, where one side of the metal clip 16 is bent downward to mechanically and electrically connected to a V-groove 18 of the pin 13. The heat dissipation performance of the single-chip package shown in FIG. 1 of U.S. Pat. No. 6,870,254B1 is good, but the heat dissipation performance of a stacked multi-chip package such as a DC-DC converter including a high-side MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) and a low-side MOSFET is poor. As shown in FIG. 2 of the present disclosure, a low-side MOSFET 25 is attached on a paddle 20, and then a metal clip 26 is attached on the top of the low-side MOSFET 25 with one side of the metal clip 26 bent downward to contact to a pin 22 located close to the paddle 20. A high-side MOSFET 27 is attached on the metal clip 26 and another metal clip 28 is attached on the top of the high-side MOSFET 27 with one side of the metal clip 28 bent downward to contact with a pin 21 located close to the paddle 20. Thus, two MOSFETs are electrically connected to the paddle 20 and the pins in a stacking structure as shown in FIG. 2. However, the chip and clip stacking structure in FIG. 2 is so thick and the heat dissipation performance is thus poor.